Writing strategy for CD-RW

ABSTRACT

An improved writing strategy for CAV writing of CD-RW is proposed and uses similar strategy as the CLV writing. The writing strategy comprises step of setting a duty ratio; obtaining a laser writing pulse duration corresponding to the duty ratio; and obtaining the duty ratio for each writing speed according to the laser writing pulse duration.

FIELD OF THE INVENTION

[0001] The present invention relates to an improved writing strategy for CD-RW, especially to an improved writing strategy for CAV (constant angular velocity) writing of CD-RW.

BACKGROUND OF THE INVENTION

[0002] The writing strategy is important issue for CD-RW (compact disc rewritable), which is applied to renew, establish and store video and audio data. The CD-RW is developed to write and erase data on various rewritable optical disk media. Therefore, the CD-RW should have suitable writing strategy such that the CD-RW is compatible to various rewritable optical disks media made by different manufacturers.

[0003] In the CLV (constant linear velocity) writing mode, the writing speed keeps constant for inner radius and outer radius of the optical disk. Therefore, when the rewritable optical disk is placed into the CD-RW, a fixed duty ratio is set for the inner radius and outer radius of the optical disk. Afterward, the jitter values for various writing speed are measured by certain instrument to ensure the jitter values are below a threshold (for example, 35). The writing strategy for each writing speed of the CD-RW can be optimized in this way.

[0004] However, for the CAV (constant angular velocity) writing mode of CD-RW, the writing speed has linear change from inner radius of the disk to the outer radius of the disk. For example, if the writing speed for inner radius is 4×speed, the center radius has 8×speed and the outer radius may have 10×speed. When the rewritable optical disk is placed into the CD-RW with CAV writing mode, the duty ratios for 4×, 8×and 10×writing speeds are set, respectively. Afterward, the jitter values for those writing speeds are measured to ensure the jitter values are tolerable. However, the duty ratios are often determined after repeated measurement. Therefore, the optical disk is segmented into several intervals with respect to writing speed and then the writing strategy is optimized for those intervals. However, this approach is complicated and time consuming for CD-RW manufacturers. Especially the writing strategy may be modified for rewritable optical disk of different manufacturers.

SUMMARY OF THE INVENTION

[0005] It is the object of the present invention to provide an improved writing strategy for CAV writing of CD-RW, which uses similar strategy as the CLV writing.

[0006] To achieve the above object, the present invention provides an improved writing strategy for CAV (constant angular velocity) writing of CD-RW. Firstly, a duty ratio is set and then a laser writing pulse duration is determined by this duty ratio. Afterward, the duty ratios for various writing speeds are deduced from the laser writing pulse duration.

[0007] The various objects and advantages of the present invention will be more readily understood from the following detailed description when read in conjunction with the appended drawing, in which:

BRIEF DESCRIPTION OF DRAWING

[0008]FIG. 1A is the timing diagram for 4×writing strategy;

[0009]FIG. 1B is the timing diagram for 8×writing strategy;

[0010]FIG. 1C is the timing diagram for 10×writing strategy.

DETAILED DESCRIPTION OF THE INVENTION

[0011]FIGS. 1A, 1B, and 1C are the timing diagram for 4×, 8×, and 10×writing strategy, respectively. At 1×speed, 1T=1/(4.3128×10⁶)=231.385 ns; wherein 4.3128×10⁶ is bit rate of the optical disk;

[0012] then

[0013] at 4×speed, 1T=1/(4.3128×10⁶×4)=57.85 ns;

[0014] at 8×speed, 1T=1/(4.3128×10⁶×8)=28.92 ns;

[0015] at 10×speed, 1T=1/(4.3128×10⁶×10)=23.14 ns.

[0016] Therefore, the duty ratios are

[0017] at 4×speed, duty ratio=Dt1/1T=Dt1/57.85;

[0018] at 8×speed, duty ratio=Dt2/1T=Dt2/28.92;

[0019] at 10×speed, duty ratio=Dt3/1T=Dt3/23.14.

[0020] The above-mentioned Dt1, Dt2 and Dt3 are laser writing pulse durations, i.e., the duration that laser writes data at those speeds. In previous situation, the parameters Dt1, Dt2 and Dt3 should be precisely adjusted. In the present invention, a specific duty ratio is set and then the corresponding laser writing pulse duration is obtained. In other word, the duty ratio at 4×speed is set firstly and then the laser writing pulse duration Dt1 at 4×speed is determined. Afterward, the Dt2 and Dt3 are set to be equal to Dt1, i.e., Dt1=Dt2=Dt3. The laser writing pulse duration is fixed for any writing speed, thus simplifying the writing strategy for CD-RW. The duty ratios now are:

[0021] at 4×speed, duty ratio=Dt1/1T=Dt1/57.85;

[0022] at 8×speed, duty ratio=Dt1/1T=Dt1/28.92;

[0023] at 10×speed, duty ratio=Dt1/1T=Dt1/23.14.

[0024] In this case, the laser writing pulse duration Dt1, Dt2, and Dt3 are independent of writing speed. The writing strategy of CD-RW can be simplified while the jitter values are quite satisfactory, as shown in following table. Writing speed tilt 3T 4T 5T 6T 7T 8T 9T 10T 11T 4x Pit jitter 27.6 28.6 27.8 27.4 29 29.2 30 30.4 30.2 Land jitter 18.4 26.8 18 20.4 21.6 22.6 22.4 23.4 26.2 8x Pit jitter 20.8 20.2 19.8 20.2 19.8 20.8 20.6 21 22 Land jitter 18 19.6 19.8 19.6 19.4 20.8 20.4 20.6 23.8 10x Pit jitter 26.8 25.4 24.8 25.6 25.4 26 27.4 26.8 26.4 Land jitter 18.8 22.4 28.4 23.6 24.4 25.2 26 25.2 28.4

[0025] Moreover, in above case, the parameter Dt1 should be globally optimized for the jitter over whole optical disk. However, if the global optimal value of Dt1 cannot be found, the disk is segmented into several virtual intervals and a local optimal value of laser writing pulse duration is searched for each interval. For example, the writing speed interval 4×-6×speed has the same laser writing pulse duration Dt1, the writing speed interval 7×-10×speed has the same laser writing pulse duration Dt2, and the difference between Dt1 and Dt2 is small. In other word, the laser writing pulse duration in one writing speed interval has same value, and has slight difference with the laser writing pulse duration in another writing speed interval. In this case, the duty ratios now are:

[0026] at 4×speed, duty ratio=Dt1/57.85;

[0027] at 6×speed, duty ratio=Dt1/38.56;

[0028] at 8×speed, duty ratio=Dt2/28.92;

[0029] at 10×speed, duty ratio=Dt2/23.14.

[0030] By this writing strategy, the jitter values are also quite satisfactory.

[0031] To sum up, the present invention provides a writing strategy for CD-RW, whereby the writing strategy for CAV writing of CD-RW is simplified.

[0032] Although the present invention has been described with reference to the preferred embodiment thereof, it will be understood that the invention is not limited to the details thereof. Various substitutions and modifications have suggested in the foregoing description, and other will occur to those of ordinary skill in the art. Therefore, all such substitutions and modifications are intended to be embraced within the scope of the invention as defined in the appended claims. 

I claim
 1. An improved writing strategy for CAV writing of CD-RW, comprising following steps: (a) setting a duty ratio; (b) obtaining a laser writing pulse duration corresponding to the duty ratio; (c) obtaining the duty ratio for each writing speed according to the laser writing pulse duration.
 2. The improved writing strategy for CAV writing of CD-RW as in claim 1, wherein in step (b), the laser writing pulse duration is a global optimal value for an optical disk; if the global optimal value cannot be found, the disk is segmented into several virtual intervals and a local optimal value of laser writing pulse duration is searched for each interval.
 3. The improved writing strategy for CAV writing of CD-RW as in claim 2, wherein the laser writing pulse duration in one writing speed interval has same value, and has slight difference with the laser writing pulse duration in another writing speed interval. 